News

Feb 6, 2012

Occupancy sensors help save energy in the workplace

Occupancy sensors can cut workplace energy costs significantly, especially when used in meeting rooms, cafeterias and even in stairwells, where safety lighting can be dimmed when people aren't present.

Occupancy sensors are one of the easiest, lowest-cost ways to save energy and cut a business's electricity bills.

Also called vacancy sensors, the devices reduce workplace energy use by turning off or dimming lights whenever people aren't present. In spaces where lights tend to be left on all day — but where people are only present part of the time — occupancy sensors can help cut significant amounts of electricity.

In recent years, occupancy sensor technology has come a long way, with advances such as wireless communication between sensors, and the development of hybrid sensors that respond to two kinds of triggers.

Tips for ensuring your sensors work properly

"Sensors can really help in terms of energy conservation," says senior Power Smart engineer Cristian Suvagau. "However, if the sensors don't integrate with the functionality of the workplace, it will limit their effectiveness, and people may even disable them."

To make the most of this energy-saving technology, here are Suvagau's top tips for putting lighting controls to work for you:

Choose the right type of sensor for the space and activity levels.

Design the sensor layout and controls to suit your purposes.

Customize settings like delay time and trigger sensitivity.

Types of sensors

There are three main types of sensors:

Passive Infrared (PIR) are the most common and least expensive type of sensor. They detect infrared radiation (heat). PIRs are fairly resistant to false triggering (turning on or off unnecessarily), but they can have "dead" spots if there are not good sight lines, for example in a bathroom or an L-shaped office space.

Ultra sonic sensors emit high-frequency beams. They tend to be more sensitive than PIRs, but are also more expensive and use a small amount of energy to emit their beams.

Acoustic, or audible sound sensors, work as if there is a microphone in the ceiling. They rarely turn off unnecessarily, but can be triggered by outside sounds or a phone ringing after hours.

According to Suvagau, some of the best sensors are "happy combinations" of these technologies. The most common of these dual-technology sensors, PIR combined with ultra sonic, is a widely applicable and increasingly popular duo.

Another hybrid pairs PIR and acoustic, which is especially effective in restrooms and storage areas where there may be sight-line obstructions for PIR sensors alone.

Ceilings or walls? Where to put sensors

Sensors can be mounted on the ceiling or on walls. Ceiling-mounted models tend to cost more, but they cover more area and so work well for larger spaces. Wall mounts are best in private offices and small rooms that don't have obstructions.

Poor placement often results in false triggering — for example placing a sensor behind the swing of a door might mean it can't detect the occupants within, or locating a private office room sensor where it will be triggered by movement in the hallway. To mitigate false triggering in an open floor plan, you can install sensors in quadrants or on distinctive project-pool workstations. Sensors can also be embedded in luminaires (light fixtures), allowing all areas to be individually controlled.

One setup doesn't fit all

One of the biggest problems with occupancy sensors is that people don't customize them for the particular needs and activities of their workplace. Settings like the delay time — how long before lights turn off — and the sensitivity of the sensor make a huge difference in how well the sensor suits the individual situation.

Sensor layouts also need to be customized. Depending on the size and configuration of a space, you will need a different numbers of sensors and a different scheme of controls.

There may be places you don't want to use sensors, or a spot where you require a manual override. Suvagau recommends interacting with the vendors to begin planning your layout.

"They are getting quite savvy about design," he says.

Best bets: meeting rooms, cafeterias, stairwells

The biggest energy savings tend to be in places that have long periods of vacancy, such as meeting rooms, cafeterias, and stairwells.

Building codes in North America dictate that you have to have minimum light in stairwells at all the times, but most sensors can trigger bi-level controls, which can turn a ballast down to 50% when it senses the area is vacant. These also work well in some hallways, for example at elementary schools with monitored hallway use.

Sensors can also be set to communicate with each other wirelessly. This is particularly useful in underground parking lots, where sensors can be set up so when one is triggered, it triggers the next light, and so on, along a determined pathway.

They can also be connected through the Internet and accessed remotely.

Involve your staff in sensor planning

One final, important element to consider is your staff. "Employees will be interacting constantly with the system," Suvagau says. "Include them from the start in decisions about the layout and controls, and continue to solicit feedback once the technology is in place."

Find out about BC Hydro's incentives for occupancy sensors and energy-efficient lighting.